It's just that a recent frequency move — designed to free up some broadcasting spectrum for new applications — will have shifted some of the free-to-air channels.

If you're in Sydney, Macarthur and Hawkesbury you should give your TV a retune now, just to be safe. If you're in Picton, Bowral and Mittagong wait until 3.30pm to retune your TVs.

The same rules apply to anyone using set-top boxes or digital recorders to get their digital signals.

The Department of Communications warns that:

There may be interruptions to all TV services today while the TV towers are being retuned. Further temporary outages may occur over the next two days. Viewers will not need to retune again after the outages — the TV services will reappear once the work at the transmission site has been completed.

If you're having any troubles, visit www.digitalready.gov.au/retune or call the Digital Ready Information Line on 1800 20 10 13. The hotline runs from 8am to 10pm AEDST, seven days a week.